This application claims the priority of German application 198 53 316.0, filed in Germany on Nov. 19, 1998.
The present invention relates to a device for damping oscillations of a winding bobbin in spinning, twisting or winding machines, comprising a bobbin holder which can be swivelled around an axle, which bobbin holder supports a rotatably supported winding bobbin, which is pressed against a drive roller, also comprising damping elements which act in the swivel direction, said damping elements comprising a friction jaw disposed by resilient forces on a friction surface, which forms a friction pairing with the friction jaw, the damping effect of which friction pairing is greater in the swivel direction when the winding bobbin is lifted from the drive roller than in the swivel direction when the winding bobbin is pressed onto the drive roller.
The idea of the damping of the bobbin holders is to suppress the winding bobbins from lifting up. Movement away from the drive roller must be intercepted, slowed down and reduced in its distance. The return movement back to the drive roller should not, in contrast, be braked. The winding bobbin should be disposed on the drive roller with a constant pressure. Thus a damping is needed which acts only when the winding bobbin is lifted suddenly from the drive roller, which damping then also acts when a spontaneous lifting motion occurs, but which immediately leaves off when the winding bobbin executes a counter-movement towards the drive roller.
A device of the above mentioned type is prior art in German published patent application 38 09 421 corresponding to British Patent Document 6B 2204334. This device comprises a tube connected to the bobbin holder for taking up a ball pivot as well as a rotatably supported connecting rod on the machine frame. A guiding holder, slidably surrounding the connecting rod, is connected to a shaft of the ball pivot. At least one friction jaw, disposed on the connecting rod, is suspended.
Thus the device, comprising a plurality of articulation points, for damping the oscillations of the winding bobbin has on the one hand a complicated design, and on the other hand is only satisfactorily effective when sufficient narrow tolerances are provided at the articulation points. After a longer period of operation, the tolerances increase, whereby the damping effect of the device is impaired.
It is an object of the present invention to create a simply designed device for damping winding bobbins, which still functions reliably after a long period of operation.
This object has been achieved in accordance with preferred embodiments of the present invention in that the friction pairing comprises a cylinder surface applied fixedly to the bobbin holder, the axis of which cylinder surface is the swivel axis of the bobbin holder, and also comprising a plane pressing surface, the resilient forces which load the pressing surface exerting a moment on the bobbin holder, which tends to lift the winding bobbin from the drive roller.
As a result of the features of the invention, a friction damping arises, which does not have the disadvantages of standard friction brakes, in which the braking effect is equal in both directions. The disadvantages explained above in association with the above mentioned prior art do not arise, whereby the damping effect is reduced with increasing operation time. It is rathermore a friction damping which is created, which makes advantageous use of a wedge effect, whereby in one swivel direction of the bobbin holder the pressing force between cylinder surface and pressing surface is increased and in the other swivel direction is weakened. The arranged effective line of the resilient force according to the present invention ensures that when the winding bobbin is suddenly lifted from its drive roller, the damping effect is suddenly increased and that in the other swivel direction the damping effect immediately decreases.
For reasons of cost-effective production it is practical when the pressing surface is arranged onto the friction jaw, and when the cylinder surface is the friction surface which acts together with the pressing surface.
In preferred embodiments of the invention, the friction jaw, preferably in the form of a wedge, is advantageously slidably supported on a sliding guide, which is arranged parallel to the line of influence of the resilient force. The sliding guide forms a wedge-shaped gap with the cylindrical surface of the bobbin holder. The wedge is drawn into the wedge-shaped gap as a result of the frictional forces arising during a swivel movement, when the winding bobbin is lifted from the drive roller, while during the other swivel movement the wedge is less firmly pressed against the cylinder surface, as the latter has the tendency to push the wedge against the effect of the spring.
The cylinder surface preferably has in circumferential direction a length which is adapted to the smallest possible and also to the largest possible diameter of the winding bobbin. This results in the same frictional and thus damping ratios, independent of the fullness of the winding bobbin, being maintained.